Medical product comprising a functional element for the invasive use in a patient&#39;s body

ABSTRACT

So as to be able to determine the position of a functional element as precisely as possible during the invasive use of a blood pump in a patient&#39;s body without the use of imaging methods, the blood pump is connected to a main sensor which records signals of the patient&#39;s heart, which are compared to other electrophysiological heart signals recorded by several sensors distributed on the body surface so as to allow the position of the blood pump to be determined by way of linking.

RELATED APPLICATIONS

This application is a U.S. National Stage filing under 35 U.S.C § ofInternational Application No. PCT/EP2012/067218, filed Sep. 4, 2012,which claims the benefit of priority to U.S. Provisional Application No.61/531,030, filed Sep. 5, 2011, and European Application No. EP11075206.0, filed Sep. 5, 2011. The contents of each of the foregoingapplications are hereby incorporated by reference in their entirety.International Application No. PCT/EP2012/067218 was published under PCTArticle 212(2) in English.

BACKGROUND OF THE INVENTION

The invention relates to the field of medical engineering, and moreparticularly to micromechanics and medical measuring technology.

Modern medicine employs microinvasive techniques in a variety of waysand to an increasing degree, so as to achieve maximum supportive,therapeutic or diagnostic success with minimal impact on the patient.

Examples of such techniques include the insertion of stents in bloodvessels, the use of thrombus filters, the removal of deposits in bloodvessels by milling, and the support or temporary or partial replacementof a patient's cardiac function through micropumps/blood pumps that areintroduced in blood vessels.

Many of these techniques require appropriate functional elements to beintroduced via the bloodstream into the patient's body by means of acatheter and to be positioned within the bloodstream in the mostexpedient manner possible.

Precise position control to as great an extent as possible is not onlydesirable, initially or during acute use, for example on a milling head,as well as in the long term, but also decisive for the success of theinvasive measure.

Positioning plays a critical role especially with blood pumps becausethese often remain in the patient's body for extended periods and mustoperate reliably without constant supervision by medical staff, whereinin the case of a catheter configuration, notably with access via afemoral artery, the risk of shifting exists due to active or passivebody movements. The precision with which blood pumps are placed is alsosubject to stringent requirements, especially when these are located inthe vicinity of a heart valve or cooperate with a heart valve.

Often times the positions of the corresponding functional elements areanalyzed using radioscopy or by means of transesophagealechocardiography. However, these methods are tied to complex devices,which are not always available. This makes the position determinationnot only complex and expensive, but in many instances it is also notpractical or useful given the extreme time pressure. While inemergencies, it is possible to place an intra-aortic pump blindly bymeasuring the distance between the puncture site in the groin and thejugular notch. However, this presupposes normal anatomic circumstancesand carries with it the risk of misplacement in the contralateralfemoral artery. This method is also imprecise because the individualanatomic features of the aorta are not predictable. If the functionalelement, in particular the pump, cannot be optimally placed, thesupporting effect of such a pump is not optimal, and other functionalelements can likewise not function optimally.

In addition to the pure transillumination method, other options areknown from the prior art for determining the position of a component,and more particularly that of a cardiac catheter, substantiallyprecisely.

U.S. Pat. No. 5,983,126, for example, discloses the application of threeorthogonal external signals outside the patient body to the positioningarea, wherein a probe is used to measure the influence of the threesignals on the functional element and thus conclude the position. Thecorresponding external signals must be designed so that they do notinterfere with the electrophysiological signals of the heart.

U.S. Pat. No. 6,226,546 B1 describes a catheter localization methodusing a plurality of acoustic probes at the catheter head, whereinsignals emitted by the probes are received via acoustic receivers andprocessed by a processing unit so as to determine the position and mapthe anatomic environment of the probes.

A catheter localization method having an accuracy of approximately 1 mmis known from U.S. Pat. No. 5,391,199, in which a transmitter outsidethe patient body emits signals by means of an antenna and receivingantennas are provided at the catheter tip, which are connected to areceiver for processing the signals. The signals are compared tocorresponding reference signals from reference antennas in the patient'sbody.

Devices and methods for recording and mapping the electrophysiologicalactivity inside a heart by means of a cardiac catheter are known fromU.S. Pat. No. 6,892,091 B1. The corresponding catheter also comprises aposition sensor, which is designed as an electromagnetic sensor. Theexemplary embodiment regarding the use of such a position sensordescribed involves the application of magnetic fields which aregenerated outside the patient body and which act on the position sensor,so that both a position and an orientation of the sensor, and thus ofthe catheter, can be determined by means of the sensor. In addition, thecomparison to reference signals of additionally introduced catheters isdescribed.

The methods known from the prior art all have complex equipment incommon, either in form of imaging devices or of additional signalsources outside the patient body. Such methods are not suitable foreveryday use that is otherwise unproblematic, with a blood pump that isoperated for cardiac support purposes for extended periods without thesupervision of medical staff.

BRIEF SUMMARY OF THE INVENTION

It is the object of the present invention to create a medical productwhich allows simple and reliable position determination during theinvasive use of blood pumps, having particularly low complexity in termsof the apparatus.

The object is achieved according to the invention by way of thecharacteristics of claim 1, 9 or 14.

The invention makes it possible to control the position of a blood pumpfor days, weeks and months, even when it is operated automatically, andeven with customary patient movements.

In the variant of claim 1, a medical product comprises a functionalelement in form of a blood pump for the invasive use in a patient'sbody, having a main sensor, which has a fixed spatial relationshiprelative to the blood pump. The main sensor in particular has a fixed,known distance from the blood pump. In addition, a processing unit isprovided, which receives signals from the main sensor representing thesignals or readings acquired by the main sensor and which determines atleast one variable representing the position of the blood pump fromsignals from the main sensor, on the basis of electrophysiologicalsignals of the heart.

It has long been known to measure electrophysiological signals on abeating heart. A typical application is the conventionalelectrocardiogram using electrodes, which are placed on a patient's skinin a suitable number, depending on the type of lead and complexity.

The time-variable signals are typically processed to form a vector whichrepresents a fingerprint characterizing the respective individual heart.Because the respective recorded electrophysiological signals are heavilydependent on the site of the lead, a comparison between a measuredsignal and a typical electrocardiogram of the same person allows aconclusion of the position of the measurement/lead. It also optionallypossible to conclude the positions of individual measuring electrodes.

To this end, the invention comprises a corresponding processing unitwhich is either directly connected to electrodes or which can besupplied with appropriately preprocessed data from ECG electrodes.

If the signals recorded by the main sensor are continually orperiodically compared or linked to the electrophysiological data of theheart, it is possible to monitor the position of the main sensor, andthus that of the functional element/the blood pump having a fixedspatial relationship therewith, on an ongoing basis. In a particularlysimple design, the main sensor is, for example, disposed on the bloodpump itself or at a fixed distance therefrom, for example at one of theends of the pump, if the blood pump is designed as substantiallyelongate body.

The method may similarly be applied using impedance measurements, or theanalysis of a pulse curve detected by the main sensor as compared to thecorresponding readings from a peripheral artery (for example arm or legartery). Here, the time delay between the pressure increase maxima andminima is measured and indicates changes of the position or of thecirculatory characteristics.

In a particular design of the invention, the processing unit can bedirectly connected to auxiliary sensors which record appropriateelectrophysiological heart signals, and the processing unit can furtherprocess the signals from the main sensor with currently detected signalsfrom the auxiliary sensors, or with data determined therefrom, forexample if the data has been preprocessed to obtain an ECG. Theadvantage of this procedure is, for example, that the temporal rhythm ofthe signals detected by the main sensor can be directly synchronizedwith the rhythm of the signals from the auxiliary sensors.

The signal obtained by way of the main sensor and the vector of the limbleads can, for example in relation to a specific limb lead in accordancewith the technique described by Goldberger, can then be utilized todefine an optimal position vector. This vector can be continuouslycompared to the ECG vector obtained by way of the main sensor, wherebythe actual position of the main sensor, and hence the position of thefunctional element, can be determined for every beat of the heart andcompared to a desired position. Data about measured vectors and datafrom the main sensor detected in this respect can be recorded forcalibration purposes with various known positions of the main sensorand/or of the functional element/of the blood pump (for example withsimultaneous use of an imaging method), and a kind of “map” of theposition can thus be stored based on exemplary data and can later becompared to currently detected data. For example, it is possible todetermine the data record that is closest to the currently detected datarecord, and the position data which is stored for this closest datarecord can be used to draw a conclusion of the current position of themain sensor and/or of the functional element.

It is also possible for the processing unit to be connected to a memoryunit in which the previously detected electrophysiological heartsignals, and more particularly those of the patient's heart, are stored,and for the processing unit to link signals from the main sensor tostored heart signals and/or to other previously detected data, or datadetermined therefrom, so as to determine the variable representing theposition of the functional element.

Temporal scaling of the data currently obtained by means of the mainsensor is then necessary, or at least advantageous, for the purpose of acomparison to the stored ECG data, before the currently obtained vectoror the currently obtained data can be compared to the stored data.

It is also conceivable to establish a relationship between the storedreference ECG data and the currently obtained ECG data from theauxiliary sensors and to obtain data on this basis, to which the signalsfrom the main sensor are compared.

The main sensor typically comprises an electrode and/or antenna forrecording electrophysiological signals. In the patient's body, suchsignals propagate electrodynamically as well as galvanically, so thatthey can be recorded well even at a distance from the heart. Thecoupling of a corresponding electrode to a measuring circuit plays adecisive role in the frequency response that is attained and whether itis a measuring electrode or an antenna.

Advantageously, it is also possible to provide more than one electrodeor antenna on the main sensor. For example, two mutually spacedelectrodes/antennas can produce a more precise determination of theposition and orientation. However, it is also conceivable to use morethan two electrodes. It is then possible to obtain a multidimensionalvector from the data detected by the main sensor.

The invention can be implemented particularly advantageously with ablood pump which can be moved through a blood vessel by means of acatheter. Information about blood pumps, which are typically usedoutside, or also inside, the heart and in which the distance from theventricle inlet or outlet or the position along the blood vessel iscrucial for successful use, can be of particular interest.

Typical functional elements according to the invention can be bloodpumps, and more particularly intra-aortic balloon pumps or rotary pumps.

The positioning relative to the ventricle is especially important withblood pumps. An intra-aortic balloon pump, for example, must bepositioned outside in front of the ventricle at a defined distance,while a rotary pump should protrude partially into the ventricle.

In this respect, according to the invention the variable representingthe position of the functional element can be the distance of thefunctional element from the mouth of a blood vessel in which thefunctional element is located into a chamber of the heart, notably alongthe course of the blood vessel.

According to a particular design of the invention, it is also possiblefor the main sensor to comprise a sensor for detecting a fluid mechanicsvariable, in particular a pressure sensor or a sensor for the flowvelocity of the blood, or it is possible for the main sensor to be sucha sensor, and it is possible for the processing unit to detect thetemporal relationship between currently detected electrophysiologicalheart signals and a measurand characterizing the blood flow at theposition of the main sensor and to determine on this basis a variablerepresentative of the position of the functional element. In this case,essentially the delay of flow modulations generated by the cardiacactivity, and more particularly of the changes in the flow velocity orpressure changes in the blood circulation system, is used to determinethe location of the main sensor or of the functional element formed by ablood pump. Because the electrophysiological signals are recordedvirtually without delay, yet the migration of a pressure wave takesplace considerably more slowly, the time delay of a pressure wavemaximum, for example, can be used to calculate the distance of the mainsensor from the heart when the migration velocity is known. Instead ofthe pressure wave maximum, it is also possible to use other typicalpoints of the pressure curve in the vascular system.

Another advantageous embodiment of the invention relates to a medicalproduct in which the processing unit detects changes in the variablerepresenting the position of the functional element and generates asignal, especially an alarm signal, when a threshold for the change isexceeded. (In the context of this patent application, “exceed” is to beunderstood as any interesting deviation from a threshold, i.e. adeviation below and/or above a certain threshold.) When an alarm signalis emitted, the patient can then seek the care of medical staff, or anadjustment can be carried out independently and automatically by meansof actuators.

Another advantageous embodiment of the invention relates to a medicalproduct in which the processing unit comprises a memory unit for adetermined position of the functional element, and a comparison unitwhich compares continuously determined position values of the functionalelement to a value stored in the memory unit, determines a differencevalue between the stored value and a currently determined positionvalue, and emits a signal if the difference value exceeds an establishedthreshold.

According to a further embodiment of the invention, the processing unitis advantageously connected to a unit which generates a signalrepresenting the current power, and more particularly the rotationalspeed of the blood pump if it is a rotary pump, and the processing unitcomprises a correction unit for taking the power of the blood pump intoconsideration in the determination of the position of the functionalelement.

In particular the rotational speed of a rotary pump can influence thecardiac function and thus influence the signals which are used for theposition determination. The influence of the rotational speed can thusbe advantageously determined, stored in characteristic fields and takeninto consideration in the evaluation.

The invention further relates to a medical product, as was alreadypartially described above by way of example, and to a method foroperating a blood pump in the body of a patient, in particular in ablood vessel, characterized in that a variable representing the positionof the blood pump is determined by a main sensor, which has a fixedspatial relationship relative to the pump, locally detecting at leastone parameter which is defined by the cardiac function of the patientand by converting the parameter into signals, and by linking identicalor additional data or signals which characterize the cardiac functionand which are detected, for example in the same blood vessel in whichthe blood pump is located, in a known position which is spaced from thepump, to the signals from the main sensor.

The invention advantageously also refers to a method for operating ablood pump in which first the blood pump is positioned in the patient'sbody at a desired location using an imaging method, characterized inthat thereafter, in accordance with the method of claim 14, a variablerepresenting the position of the blood pump is determined and stored asa calibration variable, at a later time the method in accordance withclaim 14 is carried out, and the determined variable representing theposition of the blood pump is compared to the calibration variable, anda signal is emitted if a threshold value of the variance from thecalibration value is exceeded.

The signal can be an optical and/or acoustic warning signal which isdirected to the patient or medical staff, or it can be directlyconducted to a device for adjusting the pump.

In an advantageous embodiment of the invention, the processing unit maybe designed to process signals from an impedance sensor and/or from ablood pressure sensor and/or from a respiratory activity sensor and/orfrom a sensor for the oxygen content in the blood, and/or the processingunit may be connected to one or more sensors of the aforementionedsensor types. By linking one or more of the aforementioned measurands todetected signals or measurement results of the main sensor, it is thuspossible to determine the position of the main sensor, either directlyor by way of a comparison to stored reference data. The main sensor canlikewise be suitable for detecting the aforementioned measurands, thesebeing impedance, blood pressure, respiratory activity or oxygen content.

According to one embodiment of the invention, an auxiliary sensor, whichlike the main sensor comprises a variable characterizing the bloodflood, and more particularly the variable measured also by the mainsensor, is disposed in a position, in particular in a known position,which is spaced from the unknown position of the main sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described hereafter in an exemplary embodiment andis shown in drawings.

In the drawings:

FIG. 1 is a schematic view of an intra-aortic balloon pump in a bloodvessel close to the heart, wherein the balloon takes on the compressedfrom thereof;

FIG. 2 shows the configuration of FIG. 1 with an expanded balloon;

FIG. 3 is a schematic view of the upper body of a patient withelectrodes for recording ECG signals and an intra-aortic balloon pumpcomprising a main sensor;

FIG. 4 is a schematic view of a blood vessel with a functional element,a main sensor and auxiliary sensors, and a processing unit;

FIG. 5 is a schematic view of an alternative processing unit;

FIG. 6 is a further embodiment of a processing unit;

FIG. 7 shows an alternative embodiment of the medical product accordingto the invention, comprising a pressure sensor which forms the mainsensor;

FIG. 8 shows a further alternative embodiment of the invention fordetermining the position of a functional element;

FIG. 9 shows an implantable heart pump comprising a rotor as an exampleof a functional element; and

FIG. 10 shows a medical product comprising a blood pump and a processingunit for position monitoring and an alarm system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view of a portion of a heart with a left atrium 1,a left ventricle 2, from which a blood vessel 3 extends, and heartvalves 4, which allow the blood to flow from the left ventricle 2 intothe blood vessel.

FIG. 1 shows the state in the systolic phase, in which the balloon pump5 is present with the balloon being in the compressed state. In thiscase, the balloon pump 5 forms the functional element, which can be usedto support the heart by relieving the left ventricle during acutecardiac insufficiency, coronary heart disease and similar instances.Such an intra-aortic balloon pump can be used both within the scope ofcoronary bypass surgeries when treating cardiogenic shock and acutemyocardial infarction, and with acute myocarditis, cardiomyopathy andacute left heart failure. It is typically advanced into the aortastarting from the femoral artery and is then located with the tip of thepump catheter at the end of the aortic arch. The balloon can typicallybe filled with a volume of 40 ml helium gas over a length of 20 cm andthus be expanded. The balloon is periodically filled and emptied(compressed) by an external pneumatic system. Because the balloonfilling and emptying take place counter to the cardiac activity, theafterload for the left ventricle is decreased during the systole, whichresults in an increased ejection fraction and decreased myocardialoxygen consumption.

The diastolic filling of the pump balloon, as shown in FIG. 2, displacesan average of 40 ml of blood, whereby the diastolic blood pressure israised and the organ blood flow, and the coronary blood flow inparticular, is improved during this phase.

The key in this connection is to position the functional element asoptimally as possible in the aorta relative to the heart valve 4 or themouth of the blood vessel into the left ventricle.

In this connection, as is shown in FIG. 3, the invention relates to amain sensor 6, which in the example shown is disposed at the tip of theballoon pump, however in any case is disposed in a fixed spatialrelationship, for example at a fixed, known distance thereto or directlythereon, and which allows electrophysiological signals of the heart orof a fluid mechanics variable of the ejected blood flow to be detected.The main sensor is, for example, designed as an electrode or antenna,depending on the internal circuitry, or comprises such an element.

In addition, auxiliary sensor 7, 8, 9, 10, 11 are provided, which can beformed by electrodes for ECG measurement applied externally to thepatient's body. Alternately, differently placed sensors are alsoconceivable, for example sensors which, as part of implanted devices,are not disposed on the body surface but in the body interior, but aresuitable for recording electrophysiological cardiac signals. Suchsensors can, for example, be provided in cardiac pacemakers or implanteddefibrillators.

It is also conceivable to provide a lower number of auxiliary sensors,for example one, two, three or four auxiliary sensors, wherein a highernumber allows a complex ECG vector to be attained, which allows moreprecise localization of the main sensor, and thus of the functionalelement 5, by comparison and linking to the signals from the main sensor6.

Both the main sensor 6 and the auxiliary sensors record a respectivetemporal curve of the electrophysiological cardiac signals or othermeasured variables, so that the position of the main sensor can bedetermined by comparing and linking the signals from the main sensor tothe signals of the remaining auxiliary sensors having various positions.

In addition to the functional element 12, which can be a rotary pump,for example, the corresponding main sensor 6 at the tip of thefunctional element, and the auxiliary sensors 7, 8, 9, 10, 11, FIG. 4shows a processing unit 13 in which the signals from all sensors arecombined.

In the case of ECG data, the signals from the auxiliary sensors arecombined to form a

$\quad\begin{pmatrix}{m_{1}(t)} \\\vdots \\{m_{3}(t)}\end{pmatrix}$vector, while the temporally variable signal from the main sensor 6 ispresent as a scalar f₁(t). The vector of the signals from the auxiliarysensors is compared to the function f₁ (t) so as to perform the positiondetermination of the main sensor 6 in the processing unit 13 usingpredetermined metrics and to display the result in the display device14. To this end, either the absolute distance of the functional element12 from the inlet into the left ventricle, or the spacing along theblood vessel 3 can be shown in the display device.

FIG. 5 shows an alternative embodiment of the processing unit, in whichno

$\quad\begin{pmatrix}{s_{1}(t)} \\\vdots \\{s_{n}(t)}\end{pmatrix}$currently detected electrophysiological signals are detected byauxiliary sensors and instead stored data is used. This data is storedin a memory unit 15 of the processing unit 13′ and was, for example,measured when the treatment of the patient started and was archived, soas to later allow the position of the functional element to bedetermined by comparing the currently measured signals from the mainsensor to typical signals of the patient's heart.

FIG. 6 shows a variant of the invention in which both currently measuredelectrophysiological heart signals

$\quad\begin{pmatrix}{m_{1}(t)} \\\vdots \\{m_{3}(t)}\end{pmatrix}$and stored ECG data

$\quad\begin{pmatrix}{s_{1}(t)} \\\vdots \\{s_{n}(t)}\end{pmatrix}$are linked to the signals from a main sensor. To this end, as in theexample described based on FIG. 4, the signals from the main sensor canbe recorded via several main sensor elements which are spatiallydistributed on the functional element 5, so that the main

$\quad\begin{pmatrix}{f_{1}(t)} \\\vdots \\{f_{n}(t)}\end{pmatrix}$sensor also allows a signal vector to be detected. It is then possibleto first compare the currently detected electrophysiological heartsignals

$\quad\begin{pmatrix}{m_{1}(t)} \\\vdots \\{m_{5}(t)}\end{pmatrix}$to the stored data

$\quad\begin{pmatrix}{s_{1}(t)} \\\vdots \\{s_{n}(t)}\end{pmatrix}$and link the result of this comparison to the data detected by the mainsensor, so as to output position information in the display unit 14using metrics. To this end, either an absolute distance or a trafficlight-type indicator in form of a green light for an allowed distancerange, a yellow light for a critical distance range and a red light fora prohibited distance range of the functional element from the ventriclemay be provided. As an alternative or in addition, the position may alsobe graphically represented, for example by a representation relative tothe position of the heart or of a reference point, for example of anauxiliary sensor, the position of which can in particular be exactlyknown. Moreover, the position can also be represented by means of anacoustic signal, for example an alarm signal, which indicates thedeparture from the intended position or a change in distance from apredetermined location.

FIG. 7 shows an alternative design of a medical product according to theinvention, in which a heart, which is shown symbolically and denoted bynumeral 16, simultaneously emits electrophysiological signals which arerecorded by means of one or more auxiliary sensors 7′, and bloodpressure fluctuations are transported via the vascular system due to theperiodic pump activity, wherein the fluctuations can be recorded bymeans of a pressure sensor 6′ at the tip of a functional element 5′, forexample a heart pump.

Because the electrophysiological signals are recorded by the sensors 7′virtually without delay, these convey a current picture of the cardiacactivity, which can be compared to the pressure fluctuations arriving atthe main sensor 6′ with delay due to the slower migration velocity. Itcan be determined, or it is known, at what times with regard to acomplete cardiac period certain maximal or minimal blood pressure valuesare generated in the heart, so that, having knowledge of the migrationvelocity of pressure waves, the distance of the main sensor 6′ from theventricle can be concluded from the time difference of the recording bythe sensors 6′, 7′. Using the configuration shown and a correspondingprocessing unit 13′″, it is thus possible to determine the position ofthe main sensor 6′, and thus that of the functional element 5′, relativeto the vascular system in relation to the heart and the position can bedisplayed.

The measurement is typically carried out based on the pressure maximumthat is achieved. The measurement by means of the processing unit 13′″can be calibrated when introducing the functional element 5′, forexample by slowly inserting the blood vessel while also determining theposition of the functional element 5′ by means of imaging.

FIG. 8 shows a further alternative of the medical product according tothe invention, in which a main sensor 6″, which is disposed at the tipof a functional element 5″, interacts with several, notably two, threeor four, auxiliary sensors or transceivers 17, 18, 19, 20, for examplevia magnetic fields, electrical fields or electromagnetic coupling. Acorresponding transceiver may also be used as the main sensor 6″, sothat it either transmits signals received from the elements 17, 18, 19,20, or vice versa. The intensity of the coupling of the elements 17, 18,19, 20 to the respective element 6″ can be used to determine theposition thereof relative to the elements 17, 18, 19, 20. For exampleelectrodes, which are already present and which are alternately used forposition determination and as ECG electrodes, may be used as transceiverelements 17, 18, 19, 20.

The various coupling intensities are linked in the processing unit 13″″.In this case, it is also possible for several sensor elements to bedisposed on the main sensor, for example so as to render the positiondetermination more precise or additionally allow the orientation of thefunctional element to be determined.

FIG. 9 shows a rotary pump 30 as the functional element by way ofexample, which is designed to be compressible and expandable forinsertion in a ventricle 31. The pump 30 comprises a rotor 32 having ahub 33, which can be driven by means of a drive shaft 34 from outsidethe patient body. The drive shaft is guided through a hollow catheter35, which is shown only partially. The pump 30 comprises a compressiblepump housing 36, to the proximal end of which a main sensor 37 isattached. The main sensor can be connected to a processing unit disposedoutside the body, for example via an electrical conductor located in thelumen or the housing wall of the hollow catheter 35, and notably via thedrive shaft.

During operation, the pump takes in blood via the intake cage 38 andejects the same into the blood vessel 40 via ejection openings 39. Aflexible outflow hose 41 is provided, which in cooperation with theheart valve 42, which surrounds the outflow hose, periodically closesthe ejection/outflow openings 39 and thus prevents the backflow ofblood.

This demonstrates that the position of the pump relative to the heartvalve must be precisely adhered to.

If the position of the main sensor 37 can be determined, it is alsopossible to correctly position the pump 30 in the ventricle.

In a modification, a further sensor 37 a is attached to the distal endof the pump housing. In this case, it is possible to determine acorresponding signal, for example an ECG vector, directly between thesetwo sensors and to draw a conclusion therefrom as to the position, orchange in position, of the pump. Depending on the accuracy requirementsin terms of the position determination, it may be possible in thisinstance to forego additional, notably external, auxiliary sensors.

An operating property of the blood pump may also be used to implement amain sensor which measures a fluid mechanics variable, for example theblood pressure or the flow velocity of the blood, for example in thecase of a rotary pump the current rotational speed can be used if thedriving power/torque is known, or a driving torque, driving power, orcurrent/voltage/electrical power of a driving motor of the pump.

The current rotational speed and the electrical power required fordriving purposes, which can be determined based on the drive currentrequired by the driving motor, can be used to determine the flowvelocity of the blood flow flowing through the pump in a time-resolvedmanner. When the heart is beating, this results in a periodic pattern,the phase angle of which can be compared to ECG data so as to determinethe delay of the fluid mechanics changes from the heart to the mainsensor, and thus the distance of the main sensor from the heart.

It is also possible to position two sensors in the same blood vessel,and using travel time measurements which are determined based on themeasurement of fluid mechanics variables by each of the sensors, it ispossible to determine the distance or a change in the distance of thetwo sensors. If the position of one of the sensors is fixed and/orknown, it is also possible to determine and monitor the absoluteposition of the other sensor.

FIG. 10 shows a patient body, the heart 43 of whom is supported by meansof a blood pump which is placed in the heart valve by means of acatheter 44. A sensor is disposed on the blood pump, and the signals ofthe sensor are transported by means of a line 45 extending along thecatheter 44, notably in the catheter. The signal detection takes placein a signal detection unit 46, which as an alternative or in additioncan also receive radio signals and signals from sensors in the outsideregion of the patient, for example from ECG electrodes. The signalmonitoring unit 47 monitors trends of the monitored signals and/or acomparison to reference signals for variances from threshold valuesand/or instances in which the same are exceeded. If a significant changeor variance in the position is found, a signal is emitted to the alarmsystem 48, which communicates with the outside and optionally caninitiate an adjustment of the position of the blood pump. Duringadjustment, the elimination of the alarm signal may serve as anindication that the desired position has been reached. The processingunit can also comprise a calibration system 49 for detecting and storingreference data when the desirable positioning is carried with methodsother than those that are desirable.

The medical product described in this patent application can be used forvisualizing the signals of the main sensor 6, 6′, 6″ for optimalpositioning during the implantation process, enabling easier and saferplacement of the medical product in the circulation. The visualizationmay take place on a screen of a user's console which is configured toshow the position of the medical product within the human or animalbody. The screen may be a touch screen configured to display and controlthe medical product during use. The visualization is very advantageouswith regard to control of the medical product's position in the bloodcircuit. For instance, the position of a rotary blood pump in relationto a heart valve (see, for example, FIG. 9 of the instant patentapplication) can be easily controlled by medical personnel, and anynecessary corrections can be made by repositioning the medical productaccording to the vectors displayed on the above-mentioned screen.

The invention claimed is:
 1. A blood pump, comprising: a pump housing,configured to be placed in a body of a patient, with a proximal end anda distal end, the pump housing surrounding a pump rotor coupled to thepump housing at the proximal end, wherein the rotor is drivable by adrive shaft; a main sensor, which has a fixed spatial relationship tothe pump housing, wherein at least one electrode/antenna for recordingelectrophysiological heart signals are disposed outside the body of thepatient and are configured to interact with the main sensor; and whereina processing unit is configured to determine, based on rotational speedof the rotor and electrical power delivered to the rotor, flow velocityof blood flowing through the pump housing, the flow velocity varyingover time in a periodic pattern, wherein the processing unit is furtherconfigured to determine a phase angle of the periodic pattern andcompare the phase angle to data processed from the electrophysiologicalheart signals, to determine a distance of the main sensor from a heartof the patient.
 2. The blood pump according to claim 1, wherein theprocessing unit is configured to process signals from a sensor selectedfrom a group of sensors, the group of sensors comprising an impedancesensor, an electrical sensor, a blood pressure sensor, a respiratoryactivity sensor, and a sensor for oxygen content in blood of thepatient.
 3. The blood pump according to claim 2, wherein the processingunit is connected to one or more sensors belonging to the group ofsensors.
 4. The blood pump according to claim 1, wherein the processingunit is configured to detect changes in a first variable representing aposition of the pump housing and generate a first signal when athreshold for the changes is exceeded.
 5. The blood pump according toclaim 4, wherein the generated first signal is an alarm signal.
 6. Theblood pump according to claim 1, wherein the processing unit isconfigured to: store at least one previously determined position of thepump housing, and continuously compare a currently determined positionof the pump housing to the at least one previously determined positionstored in the memory unit, determine a difference value between the atleast one stored previously determined position and the currentlydetermined position, and emit a signal if the difference value exceedsan established threshold.
 7. The blood pump according to claim 6,wherein the processing unit is configured to receive a second signalrepresenting a current power.
 8. The blood pump according to claim 7,wherein the second signal represents the rotational speed of the rotorand the processing unit is configured to take the rotational speed ofthe rotor into consideration in determining the position of the pumphousing.
 9. The blood pump of claim 1, wherein the processing unit isconfigured to compare signals recorded by the main sensor to theelectrophysiological heart signals; monitor a position of the mainsensor; and monitor, based on (i) a fixed spatial relationship to theblood pump from the main sensor and (ii) the position of the main sensora position of the blood pump.